Recording process utilizing the magnetic field of a current conducted by the record member



1949- w. A. BRASTAD ET AL 2,483,398

RECORDING PROCESS UTILIZING THE MAGNETIC FIELD OF A CURRENT CONDUCTED BYTHE RECORD MEMBER Filed March 3. 1945 2 Sheets-Sheet l BY ATTY.

Dot. 4, 1949. B STAD ET AL 2,483,398

THE MAGNETI W RECORD PRO SS U IZING C FIELD OF A U REN ONDUCTED BY THERECORD MEMBER Filed March 3, 1945 2 Sheets-Sheet 2 0 65 76 78 e4 9o 9' t8) -r -Fm\ |Mfl um 4 so J IN VE N TORS. WILLIAM A. BRASTAD LESTER F.BORCHARDT forms of recording heads for Patented Oct. 4, 1949 UNITEDsures 2,433,398 I RECORDING PROCESS UTILIZING THE MAG- NETIC FIELD OF ACURRENT BY THE REGORD MEMBER William A. Brastad and Lester Minneapolis,Minn, assignorszto ooNnporen F. Borchardt, General Mills,

This invention relates to recording sound on wire, tape, disks, and likeparamagnetic mediums.

Heretofore recordings of sound on wire have been made by transmuting theenergy of sound by means of a suitable microphone into an alternating orpulsating current which then acts through a suitable electromagnet toproduce a corresponding pulsating magnetic field through which theparamagnetic material, as wire, ribbon, disk, etc., passes to receive amagnetic recording.

By means of this invention the recording can be done Without the use ofelectromagnets or of any paramagnetic material other than that in thewire or other medium on which the record is made. Instead, the recordingis done by passing the recording current into and out of said medium.

An object of this invention is to provide a simple and efiicient methodof and apparatus for recording sound on wire.

This and other objects as will hereinafter appear, are accomplished bythis invention, which is fully described in the present application, andshown in the accompanying drawings in which Figure 1 is a diagrammaticview of the apparatus for recording sound on wire and for reproducingthe same;

Fig. 2 is an enlarged perspective view of one form of recording head foruse in this invention;

Fig. 3 is an enlarged section on the line 3 of Fig. 2;

Fig. 4 is a similar view of another form of recordin head;

Fig. 5 is an enlarged section on the line 5 of Fig. 4;

Figs. 6 and 7 are perspectives of still other use in this invention;

Fig. 8 is an enlarged section on'the line 8 of Fig. 7; and

Fig. 9 is a perspective of of recording head.

The embodiment diagrammatically illustrated in Fig. 1 consists of reelsA and B with a wire W still another form wound thereon which is unreeledfrom the reel A, passes around sheaves C, D, is wound up on the reel B.Apparatus for operating the reels A and B, to reel the wire from reel Ato reel 3, and then from reel B to reel A, is well known in this art,and is not illustrated as it forms no part of the present invention.

Sound to be recorded on the wire W, enters the microphoneE, from whichit emerges as an electric current which when suitably amplified in theamplifier F, may pass through a transformer G, receive a biasing currentfrom a suitable source such as battery H, the current then flowing inthe leads J, which acts through a recording head K to energize the wireW, as will now be described in detail. a

The recording head K may take any of the forms shown in Figs. 2, 4, 6,7, 9 and'others operating along similar lines. The recording head K inFig. 2 consists of a block lil of suitable electrical insulatingmaterial like fiber. Around this are secured two metal wire loops l2,It, which are connected to the leads J of Fig. 1. These loops serve toretain themselves on the block it and are separated at the bottom, asshown, but at the top are quite close together, preferably separated bya space N5 of approximately the diameter of the wires 52, I4 and W,namely .004". e In the present setup a stepdown transformer is used tolower the voltage and increase the magnitude of current put out by theamplifier F. The use of this transformer, however, is a matter ofchoice, depending largely on the current and voltage output of theamplifier.

For our purposes we have found that a speed of 5 it. per second on wireW is suitable both for recording and, reproducing. This, however, may bevaried considerably.

In the setup as shown in Figs. 1, 2 and 3, with the Wire W movingapproximately normal to the conductors I2, it, current enters the wire Wthrough one of the conductors 52, i l and leaves through the other.Alternations of this current in the output of the amplifier are recordedon the wire W and can be picked up, either at once or later, by asuitable electromagnetic reproducer 20, which in turn generates analternating current in the leads 22. This current then being amplifiedin the amplifier L is converted into sound in the loud speaker M.

Applicants theory of how the recording occurs, but by which they do notwish to be bound, is as follows: A biasing current preferably of theorder of one ampere is supplied to the leads J by the battery H and onthis current is superimposed a pulsating or alternating audio current bythe secondary coil of the transformer G. Referring now to Fig. 3, thesecombined currents flow through the spaced Wires l2, M and thence throughthe steel wire W on which a recording is to be made. Because of therelatively large elec tric currents and the small cross-sectional areaof the current path through the steel wire W, the magnetic fieldsgenerated by these electric currents are sufiiciently strong to leave amagnetic sound record on the moving wire. It is to be understoodapplicants are not limited to D. C. biasing but may use any other wellknown form such as supersonic.

In Fig. 4 is shown a modified form of the recording head Kl in which twothin sheets of metal 30, 32 are separated by a suitable insulator 34,and connected through leads J1 to the recording amplifier circuit ofFig. 1. The plates 30, 32 and insulator 34 are pressed between suitableinsulatin blocks 38 38 which firmly hold them in place.

The wire W1 of the circuit shown in Fig. 4, passes through a notch 39which, as shown in Fig. 5, is approximately one-half the depth of thewire. The recording by means of the apparatus shown in Fig. 4 is quitesimilar to that shown in Figs. 1 and 2. The same reproducer serves in.both cases.

In Fig. 6 is shown a pair of spaced metal electrodes 4t, 42 connectedthrough wires J2 to a suitable source of energizing current as thatsupplied by the leads J of Fig. 1, with a thin strip of permalloy or thelike 44 of the order of .002 to .020" in thickness, between them butspaced therefrom by a suitable insulator as two Scotch tape strips 55,the whole being held clamped between insulating blocks 46, 48. A wire W2similar to W of Fig. 1 slides through notches 49 in the tops of theelectrodes 40, 52 and strip 44. Thus, with current flowing fromelectrode 40 to the wire on its underside where they are in contact, theelectromagnetic field generated will largely be confined to the spacesurrounding this area particularl the area of last contact. This latteris close to the permalloy strip 44, and this strip further increases theleakage of magnetic lines of force which stray from the wire tosurrounding space thereby increasing ease with which the record ispicked up and the sound reproduced. The foregoing is the theory of whattakes place as understood by us but we do not wish to be bound by thistheory.

The recording head K3 illustrated in Fig. 7 is much like that shown inFig. 4, except that the metal electrodes 5, 52 which are also insulatedfrom each other, are relatively longer and are preferably provided withgrooves 59, for the passage of the wire W3, whose depth may beconsiderably greater than the diameter of the wire. Wire leads J: areconnected to the battery H and transformer G of Fig. 1. These electrodesare suitably secured to an insulating block 54.

In Fig. 9 is shown still another modification of the recording head K4.In this arrangement the wire Wi passes between metal rollers 60, 62which are suitably journalled on studs =64, 66, respectively, andretained by set collars E5, and set screws 61. The stud 56, is attachedto a base 63, which is secured by screws to a block of insulation 10,which in turn is secured by screws 12, to a part of the recorder frameHi. The stud 64 is carried by a member 16 which is hingedly mounted on apin 18, secured in the block of insulation '30. A spring 85, yieldablyforces the roller 60 toward the roller 52, thereby gripping the wire W4between them. The rollers can be powered so as to drive the wire W4 orthe wire can be drawn by other means thus causing the rollers to rotateabout their axes as idlers. An adjusting screw 8! is an electricinsulator to prevent current short circuiting the rollers fill, 62.

Electric current fluctuations to be recorded are made to flow to therollers 60 and 62 by means of suitable brushes 82 and 89, of carbon orthe like, held in tubular lugs 83 and 84, and yieldably, pressed againstthe peripheries of the roller by means of a spring 86, 90, adjustablyheld by screws 88 and 9|.

As the recording is made, the wire W, in Fig. 1, feeds from the reel Aover sheaves C, D and past the recording head K to the reel B. The wirecan be played by means of the reproducing head immediately afterrecording or at any later time by running the wire in the samedirection. While we have discussed only a recording medium in the formof a wire, it will be realized that this method may be satisfactorilyemployed with other forms of recording media such as tapes, disks, andcylinder.

Recordings made on this apparatus have proved to be quite satisfactory.Thus, it will be seen that we have provided very simple and eflicientforms of sound recorder and such as yield excellent records of sound onwire.

While we have shown and described but a few forms of our apparatus, itwill be apparent that it is capable of many modifications. Changes,therefore, in the construction and arrangement may be made withoutdeparting from the spirit and scope of the invention as defined by theappended claims.

We claim as our invention:

1. The method of recording sound on paramagnetic wire comprising movingthe wire at a uniform rate across electrodes closely spacedlongitudinally of the wire and in contact therewith, and impressing onthe electrodes a suitable direct current voltage and a pulsating voltageto :be recorded whereby a conduction current through the recording wirecauses the sound .to be recorded magnetically on the wire.

2. Apparatus for recording sound on paramagnetic wire comprising spacedinsulated electrodes, means for moving a wire across said electrodes andin contact therewith, means for impressing on said electrodessimultaneously a biasing voltage and a pulsating voltage to be recorded.

3. Apparatus for recording sound on paramagnetic wire comprising spacedelectrodes consisting of two thin metal plates separated by a sheet ofinsulation of the order of .003 in thickness, means for moving a wireacross said electrodes and in contact therewith, and means forimpressing on said electrodes a pulsating voltage to be recorded, thewire passing through a groove whose depth is less than the diameter ofthe wire. 7

4. The method of recording sound on paramagnetic wire comprisingdeveloping an electrical voltage corresponding to a sound to berecorded, applying the electrical voltage to closely spaced electrodes,and moving the wire longitudinally across the electrodes and in contacttherewith, whereby a varying current through the recording wire betweenthe electrodes causes the sound to be recorded magnetically on the wire.

5. Apparatus for recording sound on paramagnetic wire comprising spacedelectrodes, means for developing an electrical voltage corresponding toa sound to be recorded, means for applying said electrical voltage tothe electrodes, and means for moving a wire across the electrodes and incontact therewith, thereby causing a varying current to flow in the wirebetween the electrodes to record the sound magnetically on the wire.

6. Apparatus for recording sound on paramagnetic wire comprising spacedelectrodes consisting of two metal wires separated by a space of theorder of .003" supported by electrical insulating material, means fordeveloping a biasing voltage and a pulsating voltage corresponding to asound to be recorded, means to apply said voltages to the electrodes,and means for moving a wire across the electrodes and in contacttherewith, thereby causing a varying current to flow in the wire betweenthe electrodes to record the sound magnetically on the wire.

7. Apparatus for recording sound on paramag netic wire comprising spacedelectrodes consisting of two thin metal plates separated by a sheet ofinsulation of the order of .003" in thickness, means for developing anelectrical voltage corresponding to a sound to be recorded, means toapply said electrical voltage to the electrodes, and means for moving awire across said electrodes and in contact therewith, thereby causing avarying current to flow through the portion of the wire between theelectrodes to record the sound magnetically on the wire.

8. Apparatus for recording sound on a paramagnetic wire comprisingspaced electrodes, a strip of material highly permeable to magnetic fluxbetween said electrodes and insulated therefrom, means for developing anaudio frequency voltage corresponding to a sound to be recorded, meansfor applying said audio voltage to the electrodes, and means for movinga wire across the electrodes and strip, thereby causing a varying audiofrequency current to pass through the wire between the electrodes torecord the sound magnetically on the wire.

9. Apparatus for recording sound on a paramagnetic wire comprisingspaced electrodes, a

strip of material highly permeable to magnetic flux between theelectrodes and from, means for developing an electrical voltagecorresponding to a sound to be recorded, means for applying saidelectrical voltage to the electrodes, and means for moving a wire acrossthe electrodes and strip through a groove whose depth is less than thediameter of the wire, thereby causing a correspondingly varyingelectrical current to pass through the wire between the electrodes torecord the sound magnetically on 45 the wire.

10. Apparatus for recording sound on a paramagnetic wire comprisingspaced electrodes the thickness of which is several times the diameterinsulated theregrooves across the electrodes and strip, means for 7developing an electrical voltage corresponding to a sound to berecorded, and means for applying said electrical voltage to theelectrodes, thereby causing a correspondingly varying current in thewire between the electrodes to record the sound magnetically'on thewire.

11. Apparatus for recording sound on a paramagnetic wire comprisingspaced insulated electrodes, means for moving a wire past saidelectrodes with one electrode in contact with one point on the wire andthe other electrode in contact with a different point on the wire, meansfor developing an electrical voltage corresponding to a sound to berecorded, and means for applying said electrical Voltage to theelectrodes, thereby causing a varying current to flow through theportion of the wire between said points to record the sound magneticallyon the wire.

12. Apparatus for recording sound on paramagnetic wire comprising spacedinsulated electrodes, means for moving a wire past said electrodes withone electrode in contact with one on the wire and the other electrode incontact with a point on the wire spaced longitudinally from the firstnamed point, means for de- Veloping an electrical voltage correspondingto a sound to be recorded, and means for applying said electricalvoltage to the electrodes, thereby causing a correspondingly varyingcurrent to flow through the portion of wire between said points torecord the sound magnetically on the wire.

WILLIAM BRASTAD. LESTER F. BORCHARDT.

Country Date France Oct. 24, 1930 Number

